Rpm loss on 1996 evinrude 90 hp

[Huntfish10]

Hi everyone,
I'm new to this forum but have used it many times to help troubleshooting problems.

Last season my boat ran with no flaws. This year I saw one of my carbs was leaking and decided to do a little preventative maintenance and clean my carbs. Rebuild went good. Also changed plugs and checked for gap at .030. Motor runs great but seems to have more of a growl now than a normal 2 stroke high pitch sound.

When on the water it seems to have lost about 10 mph on top end. Takes longer to plane as well. Rpms have been dropped as well. Intermittently the boat seems to "surge" back to the high pitch and higher speed. Doesn't happen often or for long. ( split second)

When I got the boat home I checked my plugs and did find one plug very clean compared to the others. Removed plug and cranked motor to verify spark. Spark was present.

Just was out this past weekend and now seems like the motor is not charging either, could this be a coil problem or maybe even a bad plug wire?

Any help is appreciated thanks in advance

[Joe Reeves]

That very clean spark plug indicates that the cylinder is not firing. You state that you have spark (Blue flame that jumps a 7/16" gap, a strong SNAP?). Check the compression also... all cylinders should be fairly equal.

If you indeed have proper spark and compression, that leaves fuel which indicates that you've overlooked something in the carburetor that feeds that cylinder.

However, the split second you describe of having a increase on rpms, if it's a very sharp breakup in and out.... that would be ignition, in which case double check all coils and plug wires etc that might be shorting out to the powerhead.

If the engine's charging system was functioning properly previously BUT not charging after you worked on it..... was anything accidentally shorted out for a second, causing a slight spark? (Thinking possibly you might have shorted out the rectifier).

Keep in mind that the tachometer operates off of the charging system. If the charging system acts up, the tachometer will be erratic or non functional.

[Huntfish10]

Thanks for the ideas. My boat is up at my camper now but will definitely check those things out. How do I check if my coil is bad?

[Huntfish10]

Changed plug wire and plug with no good results. Noticed that my tach was not jumping at all. This motor is a e90eledr. Still missing 10mph at wot and only running at 4000 rpm. Is it possible that with the coil having 2 posts it could just be one side that is bad?

[Huntfish10]

Checked compression and all were equal. Checked spark on cylinder with the clean plug and it was at least 7/16 of an inch jump. I think my issue may be fuel related. Does anyone have any suggestions on where to start? If looking at the cylinders it is the bottom left cylinder that has the clean plug. I can see a small amount of fuel in the threads of the plug hole and the tip of the plug but the rest of the plug is very clean. Not sure if I need to continue thinking about my coil or look at my carburetor? Please help!!!!!

[Joe Reeves]

You have spark that will jump a 7/16" gap with a strong blue lightning like flame, a real SNAP on "all" cylinders?.... Stop thinking ignition!

I suggested that you had overlooked something in my first post (above). That would be where I would look first. Check for a clogged high speed jet.

Standing in back of the engine, facing the spark plugs... left is PORT, right is STARBOARD. The port bottom cylinder would be cylinder #4.

Using the term left and right is to be avoided as that varies depending of where you might be standing.

[NRGNUKE]

what model is your motor? sounds just like Joe said

[NRGNUKE]

I have had problems that didn't make sense with the floats in the past, when they got bumped or a little out. I don't think that would be your problem, but maybe your foats are closing too soon? I just like to check everything, and strangely enough often the things I wouldn't think of are the problem. lol

[Huntfish10]

My motor is E90ELEDR. It is cylinder #4 that I have the clean plug on. Heading back up to the lake Sat afternoon. Plan to get another rebuild kit for the carburetor and inspect all jets and ports. Thanks again I'll let you guys know what if find

[Huntfish10]

All cylinders do have the strong spark and compression is good as well.

[Joe Reeves]

I'm not sure if that engine has four plastic single throat carburetors or 2 aluminum dual throat carburetors.

In either case, the high speed jet is way in back of the float camber drain plug screw, located horizontally in the bottom center portion of the float chamber.

On carburetor #4, when you remove that drain plug screw, pay attention to see if fuel is actually being fed to that float chamber as a float needle valve has been known to stick occasionally.

[NRGNUKE]

just kind of thinking out loud, but is it possible that a power pack can fail to provide even distribution of power to a coil? I was wondering if a coil could fail to fire at higher rpm's but I am pretty sure nothing changes there at higher rpm's, the fire just becomes faster. Just for giggles I would swap the powerpacks and a coil with another one. pretty easy and quick

[Huntfish10]

Finally got back to the boat and pulled my carb for inspection. Immediately I noticed I forgot to install the small round gasket that goes on the stem in the middle of the float. Installed this and re***embled and boat ran like a top. Thanks for all the help!😁